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Android

How to replace a Fragment in an ActionBar in mode NAVIGATION_MODE_TABS

In the post Tab Layout in Android with ActionBar and Fragment I wrote an example about tabs in an action bar where each label open a fragment that you can not change at runtime.
In this post I explain how to replace a fragment with an other using a button.

  1. follow every step of the post Tab Layout in Android with ActionBar and Fragment
  2. add the following rows to the file values/strings.xml
        <string name="body1b">an other body one</string>
        <string name="button">open tab 1 bis</string>
        <string name="tag_bis">bis</string>
    
  3. insert a button in the linear layout in the file res/layout/tab1.xml
        <Button
            android:id="@+id/button1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/button" />
    
  4. create the file layout/tab1b.xml
    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/tab1b"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical" 
        android:gravity="center">
    
        <TextView
            android:id="@+id/textView1b"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:text="@string/body1b" />
    
    </LinearLayout>
    
  5. edit the file eu/lucazanini/Tab1Fragment.java
    package eu.lucazanini;
    
    import android.app.Fragment;
    import android.app.FragmentTransaction;
    import android.os.Bundle;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.view.ViewGroup;
    import android.widget.Button;
    import android.widget.LinearLayout;
    
    public class Tab1Fragment extends Fragment {
    
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
    	    Bundle savedInstanceState) {
    
    	LinearLayout ll = (LinearLayout) inflater.inflate(R.layout.tab1,
    		container, false);
    
    	Button button = (Button) ll.findViewById(R.id.button1);
    	button.setOnClickListener(new OnClickListener() {
    
    	    @Override
    	    public void onClick(View v) {
    		Fragment fragment = new Tab1bFragment();
    		FragmentTransaction ft = getFragmentManager()
    			.beginTransaction();
    		ft.add(android.R.id.content, fragment, getResources()
    			.getString(R.string.tag_bis));
    		ft.hide(getFragmentManager().findFragmentByTag(
    			getResources().getString(R.string.label1)));
    		ft.commit();
    	    }
    	});
    	return ll;
        }
    }
    

    the button adds the fragment with the tag “bis” and layout tab1b.xml and hides the fragment with tag “one” and layout tab1.xml

  6. create the file eu/lucazanini/Tab1bFragment.java
    package eu.lucazanini;
    
    import android.app.Fragment;
    import android.os.Bundle;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.LinearLayout;
    
    public class Tab1bFragment extends Fragment {
    
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
    	    Bundle savedInstanceState) {
    
    	return (LinearLayout) inflater
    		.inflate(R.layout.tab1b, container, false);
        }
    
    }
    
  7. replace the following methods of thew inner class TabListener in the file eu/lucazanini/TabActionBarActivity.java
    • onTabSelected
      	public void onTabSelected(Tab tab, FragmentTransaction ft) {
      	    // Check if the fragment is already initialized
      	    if (mFragment == null) {
      		// If not, instantiate and add it to the activity
      		mFragment = Fragment.instantiate(mActivity, mClass.getName());
      		ft.add(android.R.id.content, mFragment, mTag);
      	    } else {
      		// If it exists, simply attach it in order to show it
      		ft.attach(mFragment);
      	    }
      	    // if a fragment with tag "bis" exists, detach it and show the
      	    // fragment of the selected tab
      	    Fragment f = getFragmentManager().findFragmentByTag(
      		    getResources().getString(R.string.tag_bis));
      	    if (f != null) {
      		ft.detach(f);
      		ft.show(mFragment);
      	    }
      	}
      
    • onTabReselected
      	public void onTabReselected(Tab tab, FragmentTransaction ft) {
      	    // User selected the already selected tab.
      	    Fragment f = getFragmentManager().findFragmentByTag(
      		    getResources().getString(R.string.tag_bis));
      	    if (f != null) {
      		ft.detach(f);
      		ft.show(mFragment);
      	    }
      	}
      

    if you select or reselect a tab and if the fragment with tag “bis” exists then this fragment is removed and it is shown that with tag “one”

  8. launch the app
    • tab “ONE” selected
    • tab “ONE” selected + button
    • tab “TWO” selected

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